The present invention relates to organic photoconductors for electrophotography. More specifically, the present invention relates to organic photoconductors which use a cylindrical conductive substrate made of plastic material.
Recently, the so-called function-separation type organic photoconductors have been developed for electrophotography and put into market. As disclosed in the Japanese Examined Patent Publications No. S55-42380 and No. S60 34099, the function-separate type organic photoconductors have a charge generation layer on a conductive substrate, and a charge transport layer on the charge generation layer.
The charge generation layer and the charge transport layer contain organic materials as their main component. Usually, an aluminum alloy cylinder is used for the conductive substrate.
The charge generation layer is formed on the conductive substrate by coating and drying a coating liquid. The coating liquid consists of an organic solvent in which an organic charge generation agent together with a resin binder are dispersed and dissolved.
The charge transport layer is formed on the charge generation layer by coating and drying a coating liquid which consists of an organic solvent in which an organic charge transport agent together with a resin binder are dispersed and dissolved. If necessary, an antioxidant may be added to the charge transport layer.
However, image defects often occur in the above described conventional photoconductors. In more detail, image defects such as voids and grease streaks (greasing) are often caused in the normal development type electrophotographic apparatuses. Development type electrophotographic apparatuses are exemplified by plain paper copiers. Further, printing detects such as black spot and lowered contrast that frequently occur after repeated printing are often caused in the reversal development type electrophotographic apparatus. Reversal development type electrophotographic apparatus are exemplified by laser printers.
In addition, aluminum alloys used for photoconductor substrates can cause other problems. Recently, the detergent for cleaning the substrate has been switched from conventional freon detergents to aqueous detergents due to the environmental considerations such as causing the diminution of ozone in the atmosphere. However, image defects are caused by deposit residues remaining on aluminum alloys cleaned with aqueous detergents.
When the aluminum alloy substrate is coated with the charge generation layer and the charge transport layer, uneven coating is often caused by the high thermal conductivity of the aluminum alloy.
It is often necessary to roughen the substrate surface, form a light absorption layer, or form an irregular-reflection layer on the substrate to prevent interference fringes from forming on the images obtained in the electrophotographic apparatuses such as laser printers that use a white exposure light.
Although it has been a necessary objective to reduce the weight of the electrophotographic apparatuses, it is nevertheless difficult to reduce the weight of the photoconductors, since the specific gravity of the aluminum alloy is large.
Further, since the used photoconductors must be collected by specialized dealers, users cannot dispose of the used photoconductors easily.